This invention relates to a slub yarn and a process of making the same. In particular, this invention relates to a slub yarn plied with a carrier yarn, the combined yarn having high weaving performance, and a process for making it.
Slub yarns are well known in the prior art and are characterized by variations in cross section along the length of the yarn. Such yarns have been made from continuous filaments, from staple fibers and from mixtures of continuous filaments in which tufts have been incorporated, i.e., by twisting, into the continuous filament structure. When made into fabric, such yarns provide a decorative effect of slubs distributed throughout the surface of the fabric.
For some purposes, it is desirable to produce yarns having large variations in denier, particularly, with the large denier segments continuing for a considerable length along the yarn in order to obtain novel effects in fabrics for such purposes as casement fabrics, draperies, dress goods, upholstery fabrics, and the like. One of the most satisfactory yarns for such purposes in the past has been that obtained from the imperfect, freak, or double cocoons, or from cocoons of uncultivated silkworms which form imperfect silk threads. These silk yarns, called doupioni silk, are irregular and carry slubs of a thickened nature of a considerable length in an irregular fashion.
U.S. Pat. No. 3,174,271, issued to Edwards et al. on Mar. 23, 1965, discloses a variable denier multifilament yarn comprising portions of a substantially uniform base denier and an average of at least 50 slubs, per 1,000 yards (914 meters) of yarn, of continuous synthetic filaments looped upon themselves and consolidated into the yarn by filament entanglement, the slubs being of random size and distribution along the yarn, the average slub length being at least 10 inches (25.4 cm), about 10% to 30% of the slubs having lengths greater than twice the average, the slubs having an average denier ratio of at least 3.0, and about 5% to 65% of the slubs having a segment with a denier ratio of at least 10. The patent discloses that a carrier yarn can be used and that when making the slub yarn combined with a carrier yarn, the carrier yarn can be introduced at either the feed, slub, or torque jet.
U.S. Pat. No. 3,116,589, issued to Edwards et al. on Jan. 7, 1964, discloses a process for making the slub yarn of the U.S. Pat. No. 3,174,271. The process comprises continuously feeding the yarn to a supply jet, forwarding the yarn through the supply jet with a high velocity stream of compressible fluid, forwarding the yarn in the stream to impinge against a foraminous surface at an angle, continuously withdrawing the yarn from the surface at a rate at least 5% less than the rate of feed, directing a second high velocity stream of compressible fluid from a slubbing jet against the foraminous surface so that the yarn passes through the stream in a countercurrent direction to produce slubs composed of yarn loops consolidated into the yarn by filament entanglement, and collecting the slub yarn.
U.S. Pat. No. 3,296,785, issued to Hardy on Jan. 10, 1967, discloses a process for producing a slub yarn plied with a carrier yarn which comprises continuously feeding a multifilament yarn to a supply jet and forwarding the yarn in a high velocity stream of compressible fluid onto a screen surface; directing a second high velocity stream of compressible fluid from a slub jet against the screen surface to provide a turbulent zone between the two streams adjacent to the screen surface; interlacing slubs in the yarn by continuously withdrawing the yarn from the screen surface through the turbulent zone and through the slub jet in a direction countercurrent to the stream; continuously feeding a carrier yarn to the slub jet and combining the two yarns; then false twisting the combined yarns with a high velocity single vortex stream of compressible fluid, by passing the yarns through a torque jet; and interlacing the yarn plies with a high velocity, plural vortex stream of compressible fluid, by passing the combined yarns through an interlacing jet, to form a plied yarn of slub yarn and carrier yarn. The patent discloses that with respect to the torque jet and the interlacing jet either jet can precede the other. The Hardy patent describes the weaving problems which results with the use of slub yarns and indicates that the disclosed process provides a slub yarn of improved weaving performance.
U.S. Pat. No. 3,474,613, issued to Joarder et al. on Oct. 28, 1976, discloses an improved process of making an improved slub yarn which comprises the addition of a flow restricting element to the lower surface of the screen that coincides with the area where the yarn is deposited by the feed jet when using a slub process such as those set forth in U.S. Pat. Nos. 3,296,785 and 3,116,589. The product made by the disclosed process is a variable denier multifilament yarn comprising portions of substantially uniform denier and characterized by having at least 120 slubs per 1,000 yards, about 40-95% of said slubs having a segment with a denier ratio greater than about 7, about 1-10% of said slubs having a segment with a denier ratio greater than about 25, less than 1% of said slubs having a segment with a denier ratio greater than about 40.
Commercialization of some of the prior art processes has been difficult or unsuccessful. Moreover, it has been found that, when using certain of the above-described prior art processes, upon increase of productivity from less than about 366 m/min (400 yds/min) to 548-731 m/min (600-800 yds/min) the control of the slub distribution, the number of large slubs, and the cohesion of the combined yarn becomes more difficult as the productivity rate increases. Accompanying this loss of control is a decrease in the weaving performance of the resulting slub yarn. A process which provides at a high rate of productivity a slub yarn having good weaving performance and the resulting slub yarn made by said process would represent a highly desirable commercial advance. Furthermore, a slub yarn that provides the weaving performance which approaches that of an unslubbed yarn without an increase in fabric flashes or loss of fabric visual slub aesthetics would constitute a remarkable improvement over prior art material.